This invention relates generally to medical devices and, in particular, to a medical, radiotherapy source vial for containing a prescribed radiation dose for a patient.
Angioplasty is an established procedure for reducing the effect of atherosclerotic plaque on and intraluminal narrowing of the arterial walls within the vascular system of the patient. The effect is reduced by use of a catheter that is inserted into the site of the diseased-occluded vessel. A balloon portion of the catheter is then inflated to a predetermined pressure range and size, to radially compress the plaque occlusion, thereby increasing the internal diameter of the previously restricted artery. The balloon is then collapsed and the catheter is removed.
After the angioplasty procedure has been performed, as many as one-third to one-half of the patients soon develop restenosis. Restenosis can occur after angioplasty or other recannulation procedures, with or without stenting, wherein the migration and proliferation of benign cells cause a restenotic lesion to form, resulting in the further blockage of the intravascular structure.
Radiation is administered to patients for a variety of reasons, such as to treat restenosis, malignant or benign tumors, or the like. Examples of such treatments are disclosed in U.S. Pat. Nos. 5,059,166; 5,213,561; and 5,302,168.
It would be preferred to be able to provide a radiation delivery system which would:
a) deliver a predetermined totally-cumulative and homogeneous dose of radiation to the lesion site, at a predetermined penetration depth, while minimizing the exposure of surrounding healthy tissue to the radiation;
b) enable the treating physician or other health-care personnel to be bedside to the patient during the administration of the radiation therapy without exposing the physician or health care personnel to any unreasonable risk;
c) use radiation material that is readily and inexpensively available from a commercial provider;
d) use minimal special equipment storage, or delivery devices, except for routine facilities available in most nuclear medicine or radiation oncology departments;
e) use a radiation carrier material that if applied as an unsealed free-gas form, the inert, noble gas properties essentially enable the molecules of the carrier material to rapidly dissipate throughout the body of the patient without any prolonged organ accumulation or chemical interaction, and rapid dilution of the carrier material is quickly re-released from the bloodstream through the lungs;
f) minimize long term occlusion of normal blood flow during therapy, thereby providing more flexibility as to administration time and dosage;
g) use a radiation carrier material that is stable and which can be pressurized, stored, and made to high millicurie activity per cubic centimeter with reasonable cost and availability;
h) use beta particles having excellent initial dose rate delivery and energy transfer when directly adjacent to the targeted tissue within the first one millimeter, and not penetrate much beyond this depth;
i) use gamma photon energies having depth doses that provide complementary dose deposition with the beta particles for the first one millimeter, and primary additive dose delivery for an additional two to three millimeters of the targeted tissue;
j) use these beneficial physical and biological radiation properties for treating restenosis, and malignancies (for example-in the brain, lung, esophagus, trachea, cervix, biliary ductal system, colon or rectum, the gastrointestinal system, the gynecological system, or head and neck) and other internal ailments where an internal application of radiation directly applied to the tissue may be needed; and
k) attenuate the transmission dose to blood circulating through the apparatus, and while creating increased by-product radiation, delivering useful radiation dose over hundreds of micrometers of target tissue.
In order to accomplish these primary objectives, it would be desirable to have the device for delivering a therapeutic dosage of radioactive fluid to include a means to supply the treatment device with a given dosage of radioactive fluid from a source reservoir and then transfer the radioactive fluid back to the source reservoir at the completion of the treatment. Current systems for delivering radioactive gas, primarily designed for lung inhalation studies, lack the ability to retrieve the gas once it is introduced into the patient. Various syringe-type devices are known in the art for the purposes of delivering gas or inflating balloon catheters, however, they lack the safeguards necessary for working with radioactive gas, such as proper shielding and leakage prevention features that protect the patient and clinical personnel. In addition, it would be desirable to have a system whereby the standard commercially-available radioactive source vial with a pre-calibrated radioactive dosage could be directly loaded into the injection apparatus rather than relying on a standard syringe system which requires that a technician transfer or preload the radioactive material into the apparatus prior to the procedure, requiring additional handling and calibration.
The foregoing problems are solved and a technical advance is achieved in an illustrative medical, radiotherapy source vial for delivering a prescribed dose of radiation to a patient, for example, during and/or after an angioplasty procedure to inhibit, if not eliminate, restenosis and/or proliferation. The vial includes a radioactive fluid container having a contained volume for containing a prescribed dose of a radioactive fluid such as radioactive xenon gas. Advantageously, a radioactive fluid seal is disposed about the container and movable with respect to the container to change the contained volume of the container and, evacuate the radioactive fluid therein to radiation treatment apparatus. A radioactive fluid transport site such as a valve or septum is also positioned about the fluid container, which communicates with the contained volume and the exterior of the radioactive fluid container. An engagement mechanism such as a receiver is fixedly disposed about the container or seal and fixedly connectable to an external control mechansim. As a result, the contained volume in the fluid container can be decreased and increased by the actuation of the external control mechanism.
In one aspect, the radioactive fluid transport site can include a septum, a port, and/or operable valve. The engagement mechanism comprises a receiver such as a threaded arrangement for engaging with the external control mechanism. In one configuration, the fluid transport site is disposed on the radioactive fluid seal.
In another aspect of the invention, a resilient mechanism is disposed about the radioactive fluid container for urging the seal to a position in the container at which the contained volume is at an initial contained volume. In this aspect, the resilient mechanism can include by way of example a compression or tension spring.
In another aspect, the vial includes an attachment mechanism that is disposed on one or more of the container, fluid seal, or engagement mechanism. The attachment mechanism has an engaged condition and when therein maintains the contained volume fixed.
In still yet another aspect of the invention, the radioactive fluid seal is expandable and can, advantageously, include an inflatable member such as a balloon or bladder for urging the radioactive fluid from the container.